Increasingly, high metrological resolution and precision are being demanded in precision weighing technology, while simultaneously ever larger measurement ranges are to be covered by precision weighing scales. Thus products with markedly differing weights and spatial dimensions are to be weighed in continuous operation, sometimes at very high transport speeds.
Monolithically constructed weighing cells with integrated lever transmissions operating according to the principle of electrodynamic force compensation are known for use in precision scales. Such systems with single transmission are only usable up to a weight of roughly 30 kg. To extend the measurement range, a stronger magnet system can be chosen, along with the associated high costs, or the transmission ratio of the lever mechanism can be increased. In case of multiple transmissions, however, the resolution of the measurement system that can be picked up at the final lever decreases. Moreover, the production of monolithic multiple transmissions is technically elaborate and often not possible at all, due to the small amount of installation space available.
European Patent No. EP 50 708 B1 discloses a weighbridge in which the upper frame for receiving a load is coupled to a lever system, so that a pivoting or deformation of a lever section can be detected and evaluated via elongation measurement strips. The upper frame acts via two respective joints on a common lever, and the elongation measurement strips are arranged in the horizontal center of the scale.
A similar mechanism, referred to as a load sensor, is known from German Patent No. DE 69 516 860 T2. Here as well, two levers guided in the center of the scale to a force receiver are each formed over nearly the entire width of the load sensor, whereby valuable construction space in the interior of the scale or load sensor is blocked for construction. In particular, the space for additional transmission stages is thereby reduced or blocked entirely.
On the other hand, the wide design of the prior-art levers is used to reduce the sensitivity of this scale to an edge load and allows a controlled guidance of the load receiver with respect to a stationary base component of the scales.